Lamp shade stretcher attachment for sewing machines



United States Patent 1 13,550,544

{721 Inventor Martin R. Perla 1,588,001 6/1926 Becker 112/14X Fairfield, Conn. 1,906,317 5/1933 Grieb 1 12/121 18X [21] App1.No. 825,358 2,546,527 3/1951 Smyth 112/63X [22] Filed May 16, 1969 3,323,476 6/1967 Kass 112/65 [45] Patented Dec. 29, 1970 Prim ary Exammerl-l. Hampton Hunter [73] Asslgnee gzg gfi Att0rney-Herman Seid and Robert W. Fiddler [54] LAMP SHADE STRETCHER ATTACHMENT FOR 65(LastShoe),102, 121.26,121.18, 121.27, 121.24, 121.2, 12, 13, 14,15, 148; 269/(lnquired); 214/(lnquired); 223/61X, 63X,

[5 6] References Cited UNITED STATES PATENTS 1,501,710 7/1924 Grunow et a1. 112/207 ABSTRACT: A sewing machine attachment for flatbed sewing machines implementing the sewing of fabric lampshades onto a frame in which the overlapping free edges of the outer lampshade ply and liner ply, after being positioned on the shade frame are sewn together, with the outer and inner plies pulled as they are being sewn to tension the fabric on the frame. This is accomplished by arranging clamping means to grip the overlapping plies on the side of the sewing machine foot opposite the shade frame; coupling the clamping means te-shifting means for laterally shifting the clamping means engaging the overlapping plies and simultaneously permitting feeding of the overlapping plies beneath the reciprocating sewing needle; holding down by means of holding means the previously pulled overlapping plies; and bringing the clamping means back to again grip and pull the overlapping plies.

LAMP SHADE STRETCIIER ATTACHMENT FOR SEWING MACHINES BACKGROUND OF THE INVENTION This invention relates to the art of lampshade making, and more particularly to an improved attachment for conventional flatbed sewing machines implementing the manufacture of fabric lampshades on such sewing machines.

In the manufacture of fabric lampshades, present shade making techniques involve the formation of a shade frame of desired contour. Such frames are generally of a truncated conical configuration, with the frame made up of a network of wire members with an upper rim hoop separated from a lower rim hoop and held in desired position by intermediate struts extending between the hoops. The fabric shade material which may be a natural fiber, synthetic fiber, blend of synthetic and natural fiber, or in the more expensive shades a silk fabric is cut into four pieces. Two of these pieces are each of a dimension to extend over half of the interior of the shade, and when joined together form the liner of the shade. The other two pieces are each of a dimension to extend over half of the outside of the shade and are assembled to form the cover ply of the shade. First the inner or liner plies are sewn together to form the shade liner, then the outer plies are sewn together to form the shade cover. Thereafter the upper edge of the liner and cover plies are sewn together to form a skirtlike assembly. This assembled skirt is then positioned over the frame with the liner ply lying within'the frame, and the cover ply lying over the frame, this operation being referred to as top slipping."

Then, what is referred to asthe first operation" is performed, which involves the positioning of the shade with the bottom rim adjacent what is referred to as a ski presser foot on a conventional flatbed sewing machine, such as the Singer Straight Stitch 241-12. The lower frame hoop bears against the left hand side of the ski foot, with the as yet unstitched superposed liner and cover plies of the shade lying beneath the foot. In this first operation, without tension being applied, a line of stitching is extended between the cover and liner plies of the shade to secure these plies together with the shade frame sandwiched therebetween. All of these operations can be performed by the utilization of conventional sewing machine techniques, and the typical operator on this first operation is usually a woman skilled in sewing machine opera tion.

In order to effect desire positioning of the fabric plies on the lampshade frame, it is necessary to tension these plies before they are finally secured to the frame. This is accomplished by a second operation, which in the past has required relatively great strength and skill, since the sewing machine operator must exert a pull on the two plies which have been secured to the frame and simultaneously effect the sewing. The operators who perform this second sewing operation are generally men, and the availability of such male sewing machine operators, is relatively minimal, so that wages for such operators have reached a point where the production of such shades has become economically unfeasible. In this second stretching and sewing operation, the shade frame is positioned with the lower hoop against the ski shaped presser foot, with the two previously secured cover plies and liner plies extending beneath the foot. The operator manually grips the portions of the plies extending beneath the foot, exerting a pull thereon to tension the fabric on the shade frame. While the pull is exerted, the operator simultaneously rotates the shade to sew a line of stitching adjacent the bottom frame hoop, which line of stitching is closer to the frame hoop than the liner of stitching formed by the first operation. As can be understood, the problems of manually pulling the fabric, while simultaneously sewing requires relatively great strength and skill, and any relaxation of tension produces a damage in the shade resulting from crinkling, produced by the uneven tensioning. This unevenness of tensioning is further aggravated by the fact that the operator must periodically release the fabric plies which has gripped to again grip the fabric as it is being fed beneath the presser foot. Upon each release of tension by the operator. the fabric tends to return to its initial unstretched state so that the operators find it necessary to stop sewing between each step of gripping the fabric, thus slowing production.

It is with the above considerations in mind that the present improved sewing machine attachment has been evolved, serving to automatically stretch lampshade fabrics as they are being secured to a lampshade frame on a sewing machine.

It is accordingly among the primary objects of this invention to provide an improved mechanism for automatically pulling the lampshade fabric with respect to a frame as the fabrics are being sewn to the frame to effect securement of the fabric with desired tension.

Another object of the invention is to eliminate the need for relatively strong operators in performing the second stretching and sewing operation in lampshade manufacture.

A further object of the invention is to provide a sewing machine attachment which will eliminate the need for skilled sewing machine operators in providing a lampshade with desired fabric tension.

A further object of the invention is to eliminate the occur' rence of damaged shades resulting from the uneven application of tension to the shade as it is being sewn.

These and other objects of the invention which will become hereafter apparent are achieved by providing a sewing machine attachment including a clamping member movably positioned adjacent the foot of flatbed sewing machine so that it may be moved from a position adjacent the presser foot in which it clamps the plies of a fabric lampshade to a position remote from the foot tensioning the fabric, and simultaneously moving with the fabric as it is being sew. A holddown member grips the fabric immediately prior to release of the clamping action so that the clamping member may be returned to its initial position for gripping another portion of the shade fabric.

A feature of the invention resides in the provision of the a holddown member for gripping the fabric which has already been tensioned and sewn to hold same while the clamp is returned to a position for again clamping and pulling the shade fabric, thus eliminating the possiblity of any portions of the shade being improperly tensioned.

Another feature of the invention resides in the mounting of the clamp on a pivot plate whereby the clamp can be simultaneously retracted to exert the desired pull on the lamp shade fabric plies, while moving with these plies as they are being sewn.

DESCRIPTION OF THE DRAWINGS The specific details of a preferred embodiment of the invention, and their mode of functioning will be particularly pointed out in clear concise, and exact terms in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view, with parts broken away looking down at the attachment from the front showing the instant attachment in operative position as it would appear on a flatbed lockstitch sewing machine;

FIG. 2 is a top plan view of the clamping member and shifting member showing them in a solid line position as the plies of lampshade fabric are initially gripped, and in dotted line position at clamp release position immediately prior to their return; and

FIG. 3 is a schematic showing of a pneumatic system for actuating the control cylinders.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION Referring now more particularly to the drawings, the novel sewing machine attachment 10 is illustrated as applied to a conventional flatbed lockstitch sewing machine such as the Singer Straight Stitch 24 l-l2.

The machine is provided with a ski shape presser foot 12 attached to the presser foot of the machine, and the machine is provided with resilient feed dogs in a conventional fashion. The skiifoot 12 is approximately 2 inches long. three-eights of an inch wide. and three-sixteenth of an inch high. with the dimensioning determined by the size of the frames used in the lampshades being manufactured. it being preferred that the ski-foot have a thickness sufficient to provide a good bearing surface against which lower shade frame rim hoop 11 may bear.

The attachment 10. according to the illustrated embodiment is formed on plate 14 which is adapted for securement to the bed of the sewing machine.

Supported on the plate 14 is a pivot plate 16, pivoting on pivot pin 17, with the end of the pivot plate 16 remote from the pivot pin 17 free to move through an are limited by the initial clamping position and clamp release position, as will be hereinafter described.

Mounted on plate 16 for movement therewith is a lateral shift assembly 20 comprising a double acting piston-cylinder 22. The double-acting piston cylinder shift assembly 20, which is here illustratively shown as a suitable mechanism for effecting lateral shift of the hereinafter described clamp is formed with cylinder 22, supported between cylinder head blocks 23 and 23 mounted on pivot plate 16. Within the cylinder 22 is slidably arranged piston 24 secured on piston rod 25, which piston rod 25 extends through airtight seals and bushings through cylinder heads 23 and 23'. Air inlet hoses 27 and 28 are connected to air inlet ports in cylinder 22 on opposite sides of the piston 24, as a result of which the piston will be moved away from the side of the cylinder into which air is being fed, as will be understood by those skilled in the art.

According to the illustrated embodiment, a guide rod 31 is extended through a portion of the cylinder head blocks 23 and 23 a guide yoke 32 is secured to the outwardly extending end of piston rod 25. Guide yoke 32 is adjustably secured to the end of piston rod 25 by means of hex nut 33 threaded onto the end of piston rod 25, so that the position of the guide yoke 32 with respect to the cylinder block 23' may be selectively adjusted to limit the stroke of the piston 24 in cylinder 22, as will be understood by those skilled in the art.

A resilient bumper 35 is secured to the forwardly facing outer wall of cylinder 22, and a bumper detent is formed by means of angle bracket 36 secured to plate 14, with knurl headed bolt 37 threaded through an upwardly extending leg of bracket 36 to contact bumper 35, so that forward movement of the cylinder resulting from swinging movement of pivot plate 16 about pivot 17 is cushioned and adjustably limited by setting of bolt 37. The piston-cylinder shift assembly 20 on pivot plate 16 is forwardly biased (to the illustrated solid line positions) by means of spring 39 extending between spring anchor block 41 adjustably mounted on guide rod 31, and pin 42 secured and upstanding from base plate 14. As is apparent, tension spring 39 acts to bias the piston-cylinder assembly on plate 16 to a forward position.

A clamping assembly 45, as seen in FIG. 1 between ski-foot l2 and cylinder 22 is secured to the leftwardly extending portion of piston rod 25 as view in the drawing. Clamping assembly 45 is illustratively shown as formed by an anvil plate 46 against which clamp jaw 47 may be brought to bear. The anvil plate 46 is positioned so that the top thereof lies in the same plane as the top of the needleplate of the sewing machine, so that as will be understood by those skilled in the art, any fabric brought under the presser foot 12 will lie smooth over the anvil 46.

The anvil 46 is secured to a bracket 49 which is secured to the free end of piston rod 25 as seen in FIG. 1. Actuation of the clamp jaw 47 for movement against anvil 46 is accomplished in accordance with the invention by means of single acting pneumatic cylinder 50 within which spring biased piston 52 is positioned. Compression spring 53 is arranged between the bottom of cylinder 50, and piston 52 so as to exert an upward force on piston 52. Piston rod 54 is extended from piston 52 in airtight relationship through the bottom of cylinder 50 to clamp jaw 47. An air inlet hose 55 is coupled to the upper end of cylinder 50 to admit air under pressure to the cylinder 50 above piston 52. so that upon the admission of air of sufficient pressure to the cylinder 50. the piston 52 will move downwardly against the biasing action of spring 53.

Holddown means are provided adjacent to clamping means 45 to hold down the overlapping plies of liner and cover fabric employed in the lampshade after these plies have been pulled by the clamp means 45, and as the clamp means release their grip of the overlapping plies return to a position to again grasp these shade plies for further pulling and sewing. The holddown means 60 in the illustrated embodiment are formed by a yoke shaped member 62 having upper leg 63 and lower leg 64. Lower leg 64 is provided with a striated upper surface 65 against which the headed end 66 of holddown pin 67 may be brought to bear. Supported on upper leg 63 is a single acting pneumatic holddown cylinder 68, preferably formed with a spring biased piston as above-described in connection with clamp cylinder 50 in which the piston is coupled to hold down pin 67 so that upon the admission of air under pressure to cylinder 68 through air inlet conduit 69, the headed end 66 of holddown pin 67 will move against striated surface 65 to engage any material lying on the surface.

Desired operation of the cylinders is obtained as shown schematically in FIG. 3 by pneumatically coupling the cylinders to a pressure source 70 through flexible conduits. Automatic timer valve 71 coupled to the pressure source 70 is actuated to sequentially feed air to each of the cylinders.

Line pressure regulating valve 72 controls air pressure admitted to lateral shift cylinder 22. Line pressure regulating valve 73 controls air pressure admitted to clamp cylinder 50; and line pressure regulating valve 74 controls air pressure admitted to hold down cylinder 68.

According to the illustrated embodiment it is preferred that air pressure in the clamping cylinder 50 and holddown cylinder 68 be of the order of magnitude of p.s.i., whereas the pressure admitted by valve 72 to the shifting cylinder is approximately 20 p.s.i.

These pressures are varied depending on types of fabrics used, their elasticity and their tensile strength.

OPERATION In use, the aforedescribed lampshade sewing attachment 10 is secured to the bed of the conventional flatbed sewing machine, to the right of the presser foot, with the anvil of the clamping assembly 45 having its upper surface in the plane of the soleplate of the machine. Yoke adjusting hex nut 33 is positioned to limit the throw of piston 24 in shift cylinder 22. The throw of the piston 24 is adjusted, depending on the dimensioning of the shade being sew, and the type of fabric so that the desired tension will be produced in the shade fabric. The knurled bolt 37 is also adjusted to limit the pivotal movement of cylinder 22 about pivot 17.

The air hoses 27, 28, 55 and 69 are coupled to a source of air pressure valving which can either be manually, or automatically actuated to feed air into the cylinders 22, 50 and 68 to effect the desired cycle of operation, FIG. 3 showing a suggested arrangement.

The following has been found to be desired cycle:

Machine Hold needle down Shift Stitch No. position Clamp position position position Start Up Up adjacent foot Down... Left.

D do Do.

do Right Up Do. Down Do. ..do. Do.

do Left.

in operation, after the assembled liner and cover plies of the shade are sewn together, they are top slipped over the frame, and the first operation performed to join the liner and cover plies of the shade about the frame by a seam adjacent the lower rim hoop of the frame, without exerting any tension on the shade fabric.

Thereafter the shade is positioned with the lower rim hoop h adjacent ski'foot 12 (to the left as viewed in FIG. I), with the liner and cover plies of the shade extending under the foot 12, and beneath clamp jaw 47 on anvil 46. At the initiation of operation, the clamp assembly 45 is in the solid line position shown at the bottom left in FIG. 2. Upon initiation of the sewing operation by energizing the machine to effect reciprocation of the needle, air pressure is introduced into clamp cylinder 50 to force clamp jaw 47 down on the shade fabric plies resting on anvil 46 to trip these plies.

Air is fed into the shifting cylinder 22 through air inlet hose 27, to the left of shifting piston 24 to cause the clamp assembly 45, along with the shade fabric plies gripped thereby to the right as viewed in FIG. 1. The sewing action of the machine feeds the fabric simultaneously rearwardly as view in FIG. 2 and this rearward movement of the fabric is accommodated by the pivoting of the clamp assembly 45, and the shift assembly about pivot 17 to a limiting position in which the clamp as sembly 45 is adjacent the holddown assembly 60, as shown by dotted line in FIG. 2.

Hold down assembly pin 67 comes up immediately before the clamp assembly 45 reaches its limiting position to permit the fabric being sewn and pulled by the clamp assembly 45 to pass under the holddown pin. The headed end 66 of hold down pin 67 then comes downjust before release of the clamp jaw 47 under the action of air fed through into holddown cylinder 68.

The air to clamp cylinder 50 is cut off, as a result of which the biasing spring 53 forces the piston 52 up, releasing clamp jaw 47. Simultaneously, the air to the left side of shifting cylinder 22 is cut off, and air is fed into the right-hand side of the cylinder 22 to cause shifting to the shift piston 24 and clamp assembly 45 to the left, as the clamp assembly 45 and shift assembly 20 are pulled forwardly by the action of springs 39 causing pivot plate 16 to pivot about pivot 17, bringing the clamp assembly 45 to its'initial position so as to permit it again to grip the shade plies extending beneath presser foot 12.

It is thus seen that a simple sewing machine attachment has been provided serving to pull the overlapping liner and cover plies of a fabric lampshade to tension these plies about the shade frame, without requiring any special strength or skill on the part of an operator, other than would normally be required for sewing machine operation. The previous need for skillful and strong operators to apply the necessary tension has been eliminated.

Iclaim:

l. A lampshade stretcher sewing machine attachment in combination with a sewing machine having a presser foot movable down over material to be sewn positioned in the stitching area of said machine, said attachment implementing the tensioning of overlapping plies of lampshade material with respect to a lampshade frame as said plies of shade material are stitched to secure them to the shade frame. said attachment comprising: a clamp member movably positioned on said sewing machine at a point spaced from the shade frame edge on the side of the presser foot of said sewing machine opposite to the shade frame; means operating said clamp member to grip the overlapping plies of shade material; shifting means on said sewing machine coupled to said clamping member to laterally shift same with respect to said presser foot, said clamping member and said shifting means being mounted on a pivot means, which pivot means is spaced from the stitching area of the machine, whereby the clamp member may move with the material as it is being sewn. a holddown member provided adjacent and downstream of said clamp member on said sewing machine, and means operating said holddown member to grip said overlapping plies after they have been sewn together in the stitching area of the machine and fed to said holddown member to the shade material in the tensioned position when said clamp member is released for return to its initial position. j

2. The combination of claim I 111 which said clamping member and pivot means are supported on a pivot pin.

3. The combination of claim 1 in which said clamp member comprises: an anvil plate; a bracket secured to said anvil plate and having a portion spaced therefrom; a clamp jaw supported on the portion of the bracket spaced from said anvil plate; and said clamp operating means includes a piston-cylinder assembly on said bracket coupled to said clamp jaw to move same with respect to said anvil.

4. The combination of'claim 1 in which said shifting means comprise: a piston-cylinder assembly; and a piston rod extending from the cylinder of said assembly and coupled to said clamping member.

5. The combination of claim 1 in which said holddown member and said holddown member operating means comprises a pistoncylinder assembly; and a pin shaped piston rod extending from said assembly; and a plate against which an end of said rod may bear to engage the sewn plies of material.

6. The combination of claim 5 in which said piston-cylinder assembly is supported on the upper leg of a yoke shaped member having an upper and lower leg, the lower leg forming said plate.

7. The combination of claim 6 in which said plate is formed with a striated upper surface.

8. The combination of claim 4 in which said piston-cylinder assembly is double-acting. 

